The present invention relates to a fluidic apparatus.
In liquid chromatography, a fluidic sample and an eluent (liquid mobile phase) may be pumped through conduits and a column in which separation of sample components takes place. The column may comprise a material which is capable of separating different components of the fluidic analyte. Such material, so-called beads which may comprise silica gel, may be filled into a column tube which may be connected to other elements (like a control unit, containers including sample and/or buffers) by conduits.
When the internal diameter of a column is small the requested amount of fluidic flow pumped through a fluidic conduit gets very low and precise operation of the fluidic system may be difficult.
U.S. Pat. No. 6,627,075 by the same applicant Agilent Technologies discloses that volume flows of liquids in capillary tubes of chromatographic separation columns for analytical liquid measuring technology are controlled. The volume flows are derived from a liquid transport, i.e. pump arrangement, which transports a total flow to a flow splitter that divides the total flow into an excess flow in an excess path and a working flow in a working path. A controller for the working flow responds to at least one working sensor. The working sensor senses the mass flow rate of the working flow and/or the pressure in the working path which is coupled with the working sensor or the pressure differential in conduits for the excess and working flows.
U.S. Pat. No. 7,186,336 discloses a method and an apparatus for monitoring and controlling the nano-scale flow rate of fluid in the operating flow path of a HPLC system. A first flow sensor is disposed in a first flow path between a first flow-divider and a fluidic tee. A second flow sensor is disposed in a second flow path between a second flow-divider and the fluidic tee. A first recycle flow restrictor is disposed in the first recycle flow path in fluid communication with the first flow-divider. A second recycle flow restrictor is disposed in the second recycle flow path. The permeability of each recycle flow restrictor can be selected to produce a desired flow rate with each respective flow path. The output signals of the first and second flow sensors control output of a pump within each flow path.
However, the precise control of very small fluidic flows may be difficult, since pumps may be not easily scalable and adapted for delivering very small volumes.